1. Field of the Invention
The present invention relates to a method for reducing carbon dioxide.
2. Description of Related Art
A carbon dioxide (CO2) reduction technique using a catalyst is expected as a technique for fixing CO2 and producing useful substances. The reduction technique is one of the important means for solving the problem of greenhouse gas-induced global warming believed to be significant in the future. As the CO2 reduction techniques using a catalyst, a catalytic hydrogenation method and an electrochemical method (electrolytic reduction method) have been studied so far. In the catalytic hydrogenation method, CO2 reacts catalytically with hydrogen (H2) to be reduced under a high temperature and high pressure gas phase condition. The catalytic hydrogenation method allows CO2 to be converted into highly useful substances such as methanol (JP 4167775 B and JP 1 (1989)-313313 A).
In the electrolytic reduction method, the reducing reaction proceeds even at an ordinary temperature and ordinary pressure. The electrolytic reduction method requires no large-scale equipment. Thus, the electrolytic reduction method is simpler than the catalytic hydrogenation method. Accordingly, the electrolytic reduction method is considered as an effective CO2 reduction method. As catalysts capable of reducing CO2 by the electrolytic reduction method, solid single metals such as copper (Cu) and silver (Ag), alloy materials of these, and complex materials (molecular catalysts) such as a cobalt (Co) complex, a nickel (Ni) complex and an iron (Fe) complex have been developed so far (Journal of Physical Chemistry A Vol. 102 p.p. 2870 (1998), Journal of American Chemical Society Vol. 122 p.p. 10821 (2000), and Chemistry Letters p.p. 1695 (1985)).